Menace {T}: Add two mana in any combination of colors. Spend this mana only to cast Dragon creature spells. Once during each of your turns, you may cast a Dragon creature spell from your graveyard. Whenever you cast a Dragon creature spell from your graveyard, it gains "When this creature dies, exile it."
Rivendell enters the battlefield tapped unless you control a legendary creature. {T}: Add {U}. {1}{U}, {T}: Scry 2. Activate only if you control a legendary creature.
"Were I to go where my heart dwells, I would now be wandering in the fair valley of Rivendell." —Aragorn
River Delta doesn't untap during your untap step if it has a depletion counter on it. At the beginning of your upkeep, remove a depletion counter from River Delta. {T}: Add {U} or {B}. Put a depletion counter on River Delta.
"Since the war began, fishermen don't sing to the kaijin to ask for full nets. They guard the shore with thrice-blessed spears, saving the nets for their wives to pack their belongings and leave." —Hayato, master sailor
Whenever River Kelpie or another permanent enters the battlefield from a graveyard, draw a card. Whenever a player casts a spell from a graveyard, draw a card. Persist
Meet in Reverse — You draw cards from the bottom of your library rather than the top. Spoilers — Whenever an opponent scries, surveils, or searches their library, put a +1/+1 counter on River Song. Then River Song deals damage to that player equal to its power.
Imprint — Whenever a player casts an instant or sorcery spell from their hand, exile it instead of putting it into a graveyard as it resolves. At the beginning of your upkeep, if there are four or more cards exiled with River Song's Diary, choose one of them at random. You may cast it without paying its mana cost.
If {U} was spent to cast this spell, return up to one target creature to its owner's hand. If {B} was spent to cast this spell, target player reveals their hand, you choose a nonland card from it, then that player discards that card.